As various spirits and demons have been appearing on Earth to wreak havoc and cause mischief, some humans have managed to earn their loyalty through one means or another. In doing so, they gained the ability to summon them as familiars to aid or do battle for them, with some working to combat the threat and others using it for their own gain.

Among them are a 14-year old boy named Adam, partnered with a demon he named Damian, the two of them working together as self-proclaimed Demon Hunters to fight off evil spirits and protect people from harm.